Polymers of carbon monoxide and olefins, such as ethylene, have been known and available in limited quantities for many years. For example, polyketones are disclosed in Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, Vol. 12, p. 132, 1967, and in Encyclopedia of Polymer Science and Technology, 1968, Vol. 9, 397-402. It is known that polyketones may be prepared by contacting CO and ethylene monomers in the presence of a catalyst. High molecular weight polymers of ethylene which contain small quantities of carbon monoxide can be prepared with the aid of Ziegler catalysts. Low molecular weight polymers of carbon monoxide with ethylene and possible other olefinically unsaturated hydrocarbons in which all monomer units occur distributed at random within the polymer can be prepared with the aid of radical catalysts such as peroxides. A special class of the polymers of carbon monoxide with ethylene is formed by the high molecular weight linear polymers in which the monomer units occur in alternating order and which polymers consist of units with the formula --CO--(C.sub.2 H.sub.4)--. Such polymers can be prepared with the aid of, among others, phosphorus-, arsenic-, antimony-, or cyanogen-containing compounds of palladium, cobalt or nickel as catalysts.
High molecular weight linear alternating polymers of carbon monoxide and ethylene consisting of units of the formula --CO--(C.sub.2 H.sub.4)--, can also be prepared by using catalyst compositions comprising:
(a) a compound of a Group VIII metal selected from the group consisting of palladium, cobalt and nickel,
(b) a non-hydrohalogenic acid having a pKa less than 6, and
(c) a bidentate ligand of the general formula ##STR1## wherein M represents phosphorus, arsenic or antimony, R is a bivalent organic bridging group containing at least two carbon atoms in the bridge and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represent hydrocarbon groups.
Application of these catalyst compositiions to a monomer mixture which, in addition to carbon monoxide, comprises for example ethylene and one or more alkenically unsaturated hydrocarbons having the general fromula C.sub.x H.sub.y leads to the formation of polymers with units of the formula --CO--(C.sub.2 H.sub.4)-- and units of the general formula --CO--(C.sub.x H.sub.y)-- occurring randomly distributed throughout the polymer chains. The structures of the copolymers and `terpolymers` only differ in that in the case of the `terpolymers` a group --(C.sub.x H.sub.y)-- is encountered at random places in the polymer instead of a --(C.sub.2 H.sub.4)-group.
In the above-mentioned polymer preparation both the reaction rates and the molecular weights of the polymers obtained play a major role. On the one hand it is desirable to aim at the highest possible reaction rate in the polymer preparation, on the other hand,--with a view to their potential applicability--these polymers are more valuable with higher molecular weight. Both the reaction rate and the molecular weight can be affected by the temperatuure used during the polymerization process. Unfortunately, the effect the temperature has on the reaction rate is opposite to its effect on the molecular weight in that at otherwise similar reaction conditions an increase in the reaction temperature results in an increase in reaction rate, but a decrease in molecular weight of the polymers obtained. Considering the applications envisaged for these polymers this relationship will in practice resolve itself into a choice of reaction temperature which leads to polymers having molecular weights that are high enough for the relevant application and the reaction rate that goes with this temperature being a part of the bargain.